Thin-film micromesh and related methods

ABSTRACT

Thin-film mesh for medical devices and related methods are provided. The thin-film mesh may include slits to be expanded into pores, and the expanded thin-film mesh may be used as a cover for a stent device. The thin-film mesh has a tube-shape and the slits may be angled with respect to a longitudinal axis of the tube-shape thin-film mesh. The angled slits allow for the thin-film mesh to expand in multiple dimensions, including along the longitudinal axis and along the circumferential direction of the tube-shape thin-film mesh. The slits may be provided in diagonal rows arranged in longitudinal columns. Longitudinal columns of different types of slits may be arranged along the circumferential direction on the tube-shape thin-film mesh to form a zig-zag pattern of slits. The thin-film mesh may be formed from thin-film Nitinol (TFN) and may be fabricated via sputter deposition on a micropatterned wafer.

TECHNICAL FIELD

The present disclosure generally relates to medical devices and, moreparticularly, to thin-film micromeshes and related methods.

BACKGROUND

A conventional endovascular stent typically is a braided wire devicethat is compressed and delivered using a catheter and guide wire to atreatment location inside a patient. For example, the braided wiredevice may divert blood flow to reduce pressure on an aneurysm, suchthat the aneurysm no longer poses imminent danger of rupture to thepatient.

A thin-film micromesh may be used to cover the endovascular stent. Thestent may be deployed in tortuous neurovascular beds and may underundergo dramatic changes in the radial and axial dimensions during thedelivery and implantation process. Accordingly, there is a need in theart for an improved thin-film micromesh that allows for flexibility inmultiple dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic top plan view of a portion of a thin-filmmicromesh before expansion according to an embodiment.

FIG. 1B is a diagrammatic top plan views of a portion of a thin-filmmicromesh after expansion according to an embodiment.

FIG. 1C is a diagrammatic perspective side view of a thin-film micromeshdevice according to an embodiment.

FIG. 1D is a diagrammatic cross-sectional view of a blood vessel with ananeurysm in which a thin-film micromesh device is placed according to anembodiment.

FIG. 1E is a diagrammatic perspective side view of a thin-film micromeshdevice with slits or fenestrations according to an embodiment.

FIG. 1F illustrates a scenario in which a thin-film micromesh device iscontoured or bent according to an embodiment.

FIG. 2A is a diagrammatic perspective side view of a thin-film micromeshdevice with angled slits or fenestrations according to an embodiment.

FIG. 2B illustrates angled slits or fenestrations on a thin-filmmicromesh according to an embodiment.

FIG. 2C is a diagrammatic top plan view of a portion of a thin-filmmicromesh with angled slits or fenestrations according to an embodiment.

FIG. 2D is an image of a portion of a thin-film micromesh with angledslits or fenestrations according to an embodiment.

FIG. 2E is a close-up image of a portion of a thin-film micromeshaccording to an embodiment.

FIG. 2F is an image of a portion of thin-film micromesh stretched in aparticular direction according to an embodiment.

FIG. 2G is an image of a portion of thin-film micromesh stretched inanother direction according to an embodiment.

FIG. 3 is a flow diagram of a process to fabricate a thin-film micromeshfor a medical device according to an embodiment.

FIGS. 4A-Q are diagrammatic cross-sectional views of layers being formedon a substrate to fabricate a thin-film micromesh according to anembodiment.

FIGS. 5A-H are diagrammatic top plan views of layers being formed on asubstrate to fabricate a thin-film micromesh according to an embodiment.

Embodiments of the present disclosure and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures, in which theshowings therein are for purposes of illustrating the embodiments andnot for purposes of limiting them.

DETAILED DESCRIPTION

Thin-film micromeshes (also referred to as thin-film meshes) withmultiple axes of expansion and related methods are provided. Inparticular, a thin-film micromesh may include one or more slits orfenestrations arranged or orientated to form an angle with alongitudinal direction of a cylindrical-shape thin-film mesh device. Forexample, the slits or fenestrations may extend or be elongated in anangled directions with respect to the longitudinal direction of thecylindrical-shape thin-film mesh device. The angled slits orfenestrations may allow the thin-film micromesh to expand in multipledimensions, such as in radial directions and longitudinal directions ofthe cylindrical-shape thin-film mesh device. Thus, the angled slits orfenestrations allow the thin-film micromesh to be expandable andflexible in multiple dimensions.

As used herein, a thin-film mesh may be less than 100 μm (micrometers ormicrons) in thickness. In various embodiments, a thin-film mesh may beformed using fenestrated thin-film Nitinol (TFN). Other thin-film meshmaterials may be used to form the thin-film mesh disclosed herein. Thefollowing discussion is thus directed to TFN meshes without loss ofgenerality.

FIGS. 1A-E show a thin-film mesh 100, 110 and a thin-film mesh device120, a medical device including thin-film mesh 110. FIG. 1A is adiagrammatic top plan view of a portion of thin-film mesh 100 with slits102 (e.g., closed fenestrations) prior to expansion. The slits 102 maybe elongated or extend parallel to axis 106. As such, thin-film mesh 100may be expanded along axis 104, which may be referred to as axis ofexpansion 104, to open up slits/fenestrations 102. In particular,slits/fenestrations 102 may be oriented perpendicular to axis 104 andparallel to axis 106, which may be referred to as slit axis 106.Thin-film mesh 100 may be extended in directions 108 to form thin-filmmesh 110, as shown in FIGS. 1B, 1C and 1D.

FIG. 1B is a diagrammatic top plan view of a portion of thin-film mesh110 including pores 112 (e.g., open fenestrations) after expansion.Thin-film mesh 110 may be formed by expanding thin-film mesh 100 in FIG.1A. The expansion may extend thin-film mesh 100 along axis 104 such thatthere is a large increase in length along axis 104 but a small change(e.g., a small decrease) in length along axis 106. In some embodiments,the expansion may extend thin-film mesh 100 along axis 104 in a rangefrom 50% to 800%.

When expanded, slits/fenestrations 102 in FIG. 1A open up intopores/fenestrations 112 to form a “chain-link” fence pattern, such asdiamond-shaped pores/fenestrations. Thin-film mesh 110 forms strutsaround each diamond-shaped pore/fenestration 112. Alternatively,thin-film mesh 110 may be directly formed with diamond-shaped pores 112(e.g., in its final configuration or partially opened). It will beappreciated that other pore/fenestration shapes may be used in otherembodiments.

Thin-film mesh 110 may be formed, for example, as a thin-film mesh coverfor a stent backbone (e.g., backbone 122 in FIG. 1C and FIG. 2D) or as athin-film mesh scaffold for tissue engineering. Thin-film mesh 110 mayotherwise be included in a medical device for its advantageousproperties as further described herein.

FIG. 1C is a diagrammatic perspective side view of thin-film mesh device120 that includes thin-film mesh 110 and a backbone 122 (e.g., a stentbackbone). Thin-film mesh 110 expanded to its three-dimensional form(e.g., a cylindrical tube or other shape) may be assembled over backbone122, which provides structural support for thin-film mesh 110 whilemaintaining the advantageous features of thin-film mesh 110, such asfibrin deposition and cell growth (e.g., endothelialization) when placedin a blood vessel.

FIG. 1D shows a diagrammatic cross-sectional view of a blood vessel 132with an aneurysm 134 and a branch vessel 136 (e.g., a branch artery) inwhich thin-film mesh device 120 of FIG. 1C is implanted. Thin-film meshdevice 120 may advantageously be used as a flow diverter due to theproperties of thin-film mesh 110. Flow diverters may be required tostrike a balance between diverting flow from an aneurysm sac whilepermitting flow in any perianeurysmal branch vessels. Thin-film mesh 110advantageously diverts blood flow into aneurysm 134 and promotes rapiddeposition of fibrin and endothelialization at a neck 138 of aneurysm134 so that aneurysm 134 is occluded, while at the same time allowingblood flow through branch vessel 136.

Thin-film mesh device 120 advantageously has a reduced rate of delayedaneurysm rupture when compared to conventional flow diverters.Conventional wire flow diverter stents may provide occlusion of aneurysmnecks, but because the pores of such devices are often filled withparticles made up of blood coagulation products, inflammatory cells, andcellular debris, such particles may be dislodged and cause delayedaneurysm rupture. Indeed, endothelialization is slow to occur and isoften partial at best in conventional wire flow diverter stents. Incontrast, thin-film mesh 110 provides a structure on which the bloodvessel walls are rapidly rebuilt through endothelialization, promoting ahealthy and stable cellular lining, and because the cellular lining isnot prone to dislodging particles of blood coagulation products and thelike, the rate of delayed aneurysm rupture is significantly reduced.

As shown in FIG. 1E, the slits or fenestrations 102 on the thin-filmmesh 110 may be arranged to extend or be elongated in a directionparallel to a longitudinal axis 150 of the cylindrical-shape thin-filmmesh device 120. This arrangement allows the slits or fenestrations 102to expand in a circumferential direction 170 of the cylindrical-shapethin-film mesh device 120. As such, the cylindrical-shape thin-film mesh110 may expand in radial directions 160. For example, thecylindrical-shape thin-film mesh device 120 may be stored in acontracted state in which the cylindrical-shape thin-film device 120 hasa relative small diameter for delivery to a treatment site inside apatient. The cylindrical-shape thin-film mesh device 120 may then bedeployed to expand in radial directions 160 at the treatment site. Forexample, the cylindrical-shape thin-film device 120 may expand radiallyto have a larger diameter to press on and attach to an inner wall of ablood vessel. Thus, thin-film mesh 110 with slits or fenestrations 120that extend along a direction parallel to the longitudinal axis 150 ofthe cylindrical-shape thin-film device 120 allows for expansion inradial directions 160.

However, such slit or fenestration arrangement results in limitedexpansion or flexibility in the longitudinal direction 150 of thecylindrical-shape thin-film device 120. For example, the thin-filmdevice 120 may be deployed in tortuous neurovascular beds and mayundergo dramatic changes in both radial and longitudinal dimensionsduring the delivery and implantation process.

FIG. 1F illustrates a scenario in which the cylindrical-shape thin-filmdevice 120 is contoured or bent into a U shape. The U-shape may berequired to conform to a particular treatment location in a patient. Theinner radius r of the U-shape may be about 6.37 mm, the outer radius Rof the U-shape may be about 10.37 m, and the diameter of thecylindrical-shape thin film device 120 may be about 4 mm. In suchscenario, the outer curve (about 32.6 mm) may be about 63% longer thanthe inner curve (about 20 mm). To conform to such treatment location,the outer curve side of the cylindrical-shape thin-film device 120 wouldhave to expand about 63% more than the inner curve side along thelongitudinal direction 150 of the cylindrical-shape thin-film device120. Thus, the cylindrical-shape thin-film device 120 that expandsmainly in the radial directions and has limited expandability orflexibility in the longitudinal direction may not meet suchrequirements.

Accordingly, an improved thin-film micromesh that allows for flexibilityin multiple dimensions is proposed. For example, the improved thin-filmmicromesh may have slits or fenestrations that are arranged to extend orbe elongated in a direction that forms an angle with a longitudinal axisof a cylindrical-shape thin-film device. In particular, the angled slitsor fenestrations may allow the thin-film micromesh to expand both in theradial directions and along the longitudinal axis of thecylindrical-shape thin film device.

FIG. 2A illustrates a perspective view of a thin-film mesh device 220provided with an improved thin-film mesh 210 that allows for flexibilityand expansion in multiple dimensions. Thin-film mesh 210 may include aplurality of angled slits or fenestrations 202. In particular, slits orfenestrations 202 may be elongated or may extend in directions that formangles (e.g., not parallel) with the longitudinal axis 150 ofcylindrical-shape thin-film mesh device 220. The angled slits orfenestration allow thin-film mesh 210 to expand in a circumferentialdirection 170 of cylindrical-shape thin-film mesh device 220. Suchcircumferential expansion allows the cylindrical-shape thin-film meshdevice 220 to expand in radial directions 160. The angled slits orfenestration also allow thin-film mesh 210 to expand along thelongitudinal axis 150 of the thin-film mesh device 220. Expansion in thelongitudinal axis 150 allows the thin-film mesh device 220 to beflexible along the longitudinal axis 150, such that the thin-film meshdevice 220 may bend or contour during the delivery process and conformto various shapes of treatment locations in patients.

FIG. 2B illustrates different types of angled slits or fenestrations ina thin-film mesh. For example, thin-film mesh 210 may have at least twodifferent types of slits or fenestrations 202 a and 202 b. Each of thefenestrations or slits 202 a and 202 b may be surrounded and formed bycorresponding struts 116. For example, the fenestrations or slits 202 aand 202 b may each have an elongated oval shape including semicircles ontwo ends and two parallel sides. Other shapes of slits or fenestrationsmay be used based on the particular application of the thin-film meshdevice 220.

Surrounding struts 116 may have a strut width between 1 and 25 μm. Eachof slits/fenestrations 202 a and 202 b may have a slit length of between25 μm and 500 μm. Different types of slits or fenestrations may havedifferent slit dimensions, such as different lengths, widths, shapes,and the like. For example, the slit lengths may be modulated based onthe type of medical device, the type of medical treatment, the bodyregion being treated, and/or the type of aneurysm being treated. In someembodiments, the slit lengths of slits 202 a and 202 b may be between 50μm and 300 μm (e.g., between 50 μm and 225 μm, or between 50 μm and 200μm) to provide thin-film mesh device 220 with advantageous features suchas fibrin deposition and cell growth (e.g., endothelialization) whenplaced in a blood vessel.

Slit 202 a may extend or be elongated along a slit axis 206 a. As shownin FIG. 2B, slit axis 206 a may form an angle a with the longitudinalaxis 150 of the cylindrical-shape thin-film mesh device 220. Slit 202 amay expand along an expansion direction 108 a. Expansion direction 108 amay be perpendicular to the slit axis 206 a. Thus, slit 202 a may beexpanded diagonally in the expansion direction 108 a, which has vectorcomponents in both the circumferential direction 170 and thelongitudinal direction 150. As such, the diagonally expanding slit 202 amay allow thin film mesh 210 to expand in both the circumferentialdirection 170 and the longitudinal direction 150.

As the angle a increases, the vector components of the expansiondirection 108 a increases along the longitudinal direction 150 anddecreases in the circumferential direction 170. Thus, the slit 202 a maybecome more expandable in the longitudinal direction 150 and lessexpandable in the circumferential direction 170. As the angle adecreases, the vector components of the expansion direction 108 adecreases along the longitudinal direction 150 and increases in thecircumferential direction 170. As such, the slit 202 a may become moreexpandable in the circumferential direction 170 and less expandable inthe longitudinal direction. Thus, the angle a of slit 202 a may bedetermined and adjusted based on the particular application and use forthe thin film micromesh 210 (e.g., radial expandability v. longitudinalexpandability).

Similarly, slit 202 b may extend or be elongated along a slit axis 206b, which forms an angle b with the longitudinal axis 150 of thecylindrical-shape thin film mesh device 220. Slit 202 b may expand alongan expansion direction 108 b, which is perpendicular to the slit axis206 b. Thus, similar to slit 202 a, slit 202 b also allows for diagonalexpansion of thin film mesh 210, but they have different diagonalexpansion directions.

In some embodiments, slit 202 a and slit 202 b may complement eachother. For example, slits 202 a and 202 b may be angled from thelongitudinal axis 150 by the same amount (e.g., angle a=angle b), but inopposite directions. As shown in FIG. 2B, slits 202 a and 202 b may bemirror image of each other with respect to the longitudinal axis 150.Slits that are different but complement each other in this manner mayallow for symmetrical and/or uniform expansion of thin film micromesh210. This may prevent undesired wrinkles or ripples in the thin filmmicromesh 210 when expanded.

As shown in FIG. 2C, different types of slits or fenestrations 202 withdifferent orientations and arrangements may be provided on the thin filmmesh 210. Slits or fenestrations with the same orientation may begrouped together in rows and columns. For example, slits with the sameangles may line up in a diagonal row 225. As such, slits 202 arranged inthe same diagonal row 225 have the same slit axis, which forms the sameangle with the longitudinal axis 150. Diagonal rows 225 of the sameslits may be arranged in parallel to each other to form a longitudinalcolumn 235. Different types of slits 202 may be arranged in differentlongitudinal columns 235 in thin-film micro mesh 210.

As shown in FIG. 2D, a first type of slits may be provided in first typelongitudinal columns 235 a and 235 c and a second type of slits may beprovided in second type longitudinal columns 235 b and 235 d. The firsttype longitudinal columns 235 a and 235 c and the second typelongitudinal columns 235 b and 235 d may be arranged to alternate in thecircumferential direction 170. For example, a first type longitudinalcolumn 253 b is provided between two adjacent second type longitudinalcolumns 235 a and 235 c. This provides a zig-zag pattern of slitsbetween different longitudinal columns. In some embodiments, thelongitudinal columns may have the same width and the slits 202 ofadjacent longitudinal columns may complement each other (e.g., mirrorimage of each other). This provides symmetrical and/or even expansion ofthe thin film micromesh 210, which prevents undesired wrinkles orripples in the thin film micromesh 210.

FIG. 2E illustrates a close-up view of a portion of the thin-film micromesh 210. Slits 202 may be formed by surrounding struts 116. Forexample, struts 116 may form diagonal rows of slits 202. Slits 202 ofadjacent diagonal rows may be staggered in an overlapping manner. Forexample, as shown in FIG. 2E, slit 202 c may be staggered from slit 202d in the adjacent diagonal row. Staggering slits 202 in adjacentdiagonal rows may provide an overall chain link pattern in the thin filmmicro mesh 210 that allows the thin-film micro mesh 210 to expandeffectively.

Adjacent longitudinal columns 235 may have different types of slits 202.For example, as shown in FIG. 2E, longitudinal column 235 e has slits202 that angled differently from slits in longitudinal column 235 fV-shaped slits 250 may be formed between two different types oflongitudinal columns 235 e and 235 f. A V-shaped slit 250 may be formedby portions of two different types of slits 202 e and 202 f. An angle252 may be formed between the slit axes of the two different types ofslits 202 e and 202 f. The angle 252 may determine the expandability ofthe thin-film micromesh 210 to in the circumferential direction 170 ascompared to the longitudinal direction 150. For example, a larger angle252 may increase the expandability of the thin film micromesh 210 in thelongitudinal direction 150 while decrease the expandability of thin filmmicromesh 210 in the circumferential direction 170. A smaller angle 252may decrease the expandability of thin film micromesh 210 in thelongitudinal axis 150 while increase the expandability of the thin filmmicromesh 210 in the circumferential direction 170. The angle 252 may bedetermined and adjusted based on the particular application and use forthe thin film micromesh 210.

Further, the ability of thin-film mesh 210 to effectively expand maydepend on the lengths of slits 202. Slits 202 with longer slit lengthshave greater ability for expansion, while slits 202 with a shorter slitlength have less ability for expansion. The dimension of slits 202 alsomay define the pore density of the thin film mesh micro 210. In someembodiments, thin-film mesh 210 has a pore density (fenestrations persquare mm) of between 15 pores/mm² and 2217 pores/mm², and a percentmetal coverage (PMC) of between 6% and 83%. In some embodiments, thinfilm mesh 210 has a high pore density (e.g., 50 pores/mm²-3000pores/mm²) and a low metal coverage (e.g., 10%-35%), which mayadvantageously promote a planar deposition of fibrin followed by rapidcell growth (e.g., endothelialization).

FIG. 2E illustrates a thin-film micro mesh 210 in a non-expanded state.FIG. 2F illustrates that the thin-film micro mesh 210 is stretchedmainly in the circumferential direction 170. The circumferential stretchmay allow the thin-film micro mesh device 220 to expand in the radialdirections 160. FIG. 2G illustrates that the thin-film micro mesh 210 isstretched mainly in the longitudinal direction 150 of the thin-filmmicro mesh device 220. The slits 202 may open up to form diamond-shapedpores 212. The longitudinal stretch may allow the thin-film micro meshdevice 220 to expand and/or be flexible along the longitudinal axis 150.

The thin-film micro mesh 210 may be customized to have a particularcombination of parameters based on a particular application thethin-film micro mesh 210. For example, the angle 252 (e.g., anglea+angle b) formed between slit axes may be adjusted to change theexpandability of the thin-film micro mesh 210 in the circumferentialdirection 170 versus the longitudinal axis 150. The size and dimensionof the slits 202 also may be adjusted. For example, a longer slit lengthmay increase the expandability of the slits 202.

In some embodiments, the size of longitudinal columns and/or the numberof slits in a diagonal row also may be adjusted to increase or decreasethe force required to expand the micro mesh 210. For example, increasingthe number of slits 202 in a diagonal row 235 may decrease the forcerequired to expand the micro mesh 210. The width or thickness of thestruts 116 also may be adjusted to increase or decrease the percentagemetal in the micro mesh 210 and/or the force required to expand themicro mesh 210. For example, wider and/or thicker struts 116 mayincrease the percentage metal and/or increase the force required forexpansion.

FIG. 3 is a flow diagram of a process 300 to fabricate a thin-film mesh,such as thin-film mesh 210 of FIGS. 2A-2G, for a thin-film mesh device,such as thin-film mesh device 220. At block 302, trenches are formed ona wafer 400 (e.g., a silicon wafer or other wafer) as shown in FIGS.4A-4E and 5A-5C. FIGS. 4A and 5A show wafer 400, which may have an oxidelayer with a thickness of between 500 nm and 1 μm on top. A photoresist402 is spun-coated on wafer 400 as shown in FIG. 4B. By patterning anddeveloping photoresist 402 using photolithography, a pattern of exposedareas 404 is formed as shown in FIG. 4C and FIG. 5B. The pattern maydefine rows and columns of angled slits 202. The pattern of exposedareas 404 is available for etching. Deep reactive ion etching (DRIE) isperformed to form grooves or trenches 406 that are at least 15 μm deep(e.g., between 25 μm and 200 μm deep) as shown in FIG. 4D. Photoresist402 is removed and wafer 400 is cleaned, resulting in etched wafer 400with trenches 406 as shown in FIG. 4E and FIG. 5C. Trenches 406 may forma micropattern that provides a template for thin-film mesh 210. Forexample, the micropattern may define slits 202 in diagonal rows 225 andlongitudinal columns 235, as shown in FIGS. 2A-2E. The resolution of themicropattern using the DRIE process may be, for example, approximately 1Although two micropatterns 502 for two thin-film meshes are shown inFIG. 5C, wafer 400 may include more micropatterns. The term“approximately,” as used herein when referring to a measurable value,encompasses variations of ±20%, ±10%, ±5%, ±1%, ±0.5%, or ±0.1% of thevalue.

At block 304, a sacrificial layer 408 (e.g., a chrome sacrificial layeror a copper sacrificial layer), also referred to as a lift-off layer, isdeposited as shown in FIG. 4F. Sacrificial layer 408 may be deposited bysputter deposition or evaporation deposition such as electron beamphysical vapor deposition (EBPVD). Sacrificial layer 408 may have athickness of, for example, 1 μm or less (e.g., approximately 500 nm).

At block 306, a Nitinol layer 410 is deposited as shown in FIG. 4G andFIG. 5D. Nitinol layer 410 may have a thickness of, for example, between1 μm and 20 μm (e.g., approximately 5 μm). As sputtered Nitinol atregions corresponding to trenches 406 fall to the bottom of trenches406, the micropattern of trenches 406 of wafer 400 are duplicated onNitinol layer 410 as corresponding fenestrations (e.g., closedfenestrations) such as slits 202 of thin-film mesh 210 as shown in FIGS.2A-2E. The resulting pattern of fenestrations 202 may also be denoted asa fiche in that fenestrations 202 are in closed form prior to anexpansion of thin-film mesh 210. Just like a microfiche, each fiche orpattern of fenestrations 202 effectively codes for resultingfenestrations when thin-film mesh 210 is expanded to fully open upfenestrations 202.

At block 308, a shadow mask 412 is applied as shown in FIG. 4H. Shadowmask 412 is applied to a mesh region 414 and exposes seam regions 416for deposition of a bonding layer 418.

At block 310, bonding layer 418 (e.g., an aluminum bonding layer) isdeposited as shown in FIG. 4I. Bonding layer 418 may have a thicknessof, for example, 1 μm or less (e.g., approximately 500 nm).

At block 312, shadow mask 412 is removed as shown in FIG. 4J.

At block 314, a shadow mask 420 is applied as shown in FIG. 4K. Shadowmask 420 is applied to seam regions 416 and exposes mesh region 414 fordeposition of a sacrificial layer 422.

At block 316, sacrificial layer 422 (e.g., a chrome sacrificial layer ora copper sacrificial layer) is deposited as shown in FIG. 4L and FIG.5E. Sacrificial layer 422 may have a thickness of, for example, 1 μm orless (e.g., approximately 500 nm).

At block 318, shadow mask 420 is removed as shown in FIG. 4M.

At block 320, a Nitinol layer 424 is deposited as shown in FIG. 4N andFIG. 5F. Nitinol layer 424 may have a thickness of, for example, between1 μm and 50 μm (e.g., approximately 5 μm). Similarly to block 306, assputtered Nitinol at regions corresponding to trenches 406 fall to thebottom of trenches 406, the micropattern of trenches 406 of wafer 400are duplicated on Nitinol layer 424 as corresponding fenestrations(e.g., closed fenestrations) such as slits 202 of thin-film mesh 210 asshown in FIGS. 2A-2E.

At block 322, a protective layer 426 (e.g., a protective chrome layer)is deposited as shown in FIG. 4O. Protective layer 426 may have athickness of, for example, 1 μm or less (e.g., approximately 500 nm).

At block 324, Nitinol layers 410, 424 and bonding layer 418 are annealedto form thin-film mesh 210 as shown in FIG. 4P. Wafer 400 with Nitinollayers 410, 424 and bonding layer 414 may be annealed at a hightemperature (e.g., approximately 675° C. for approximately 10 minutes)to melt bonding layer 418 and crystalize amorphous Nitinol layers 410,424. Nitinol layer 410 and Nitinol layer 424 are fused in inseam region416.

At block 326, thin-film mesh 210 is released as shown in FIG. 4Q andFIG. 5G. Annealed wafer 400 may be placed in chrome etchant (e.g., forapproximately 1 hour) to release thin-film mesh 210 from top of thewafer 400.

At block 328, thin-film mesh 210 is expanded to form a three-dimensionalthin-film mesh 210 with angled fenestrations 202 that have been openedup such as a cylindrical tube as shown in FIG. 5H. It will beappreciated that combining the lift-off process with multiple-layerdepositions of Nitinol separated by layers of sacrificial layers enablesfabrication of thin-film meshes 210 of various other three-dimensionalshapes in other embodiments.

A thin-film micro mesh membrane, or a corresponding hybridmembrane/structure may be used for various medical treatments asdescribed below.

In some embodiments, a thin-film mesh membrane may be used at varioustreatment locations in a patient, such as in various types ofneurovasculature, carotid vascular beds, cardiac vascular beds, aorticvascular beds, iliac vascular beds, renal vascular beds, peripheralvascular beds, upper extremity vascular beds, and other similartreatment locations.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used, forexample, for to facilitate wound healing for burns, pressure ulcers,scar revisions, ischemic lower limb ulcers and other acute and chronicwounds.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used tostop acute bleeding whether from injury or from surgical intervention(“hemostasis”).

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used tofacilitate bone healing that is wrapped around or placed within afracture site, or is wrapped around structural elements formed of othermaterials (e.g. titanium) that bridge a gap between bones.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used togrow human chondrocytes and create a thin plate of cartilage. Thiscartilage plate could be used in joint operations to delay knee or hipreplacement or other osteoarthritic conditions.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used todeliver chemotherapeutics directly to the site of a tumor followingsurgical excision of the tumor.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used incardiac surgery to place cardiac myocytes at a site of myocardialinfarction. Following infarct the surgeon would excise the scarred areaand insert the membrane or the hybrid membrane to facilitate regrowth ofhealthy tissue as opposed to scar tissue that typically accompaniesmyocardial infarction.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used as ascaffold device for nerve regrowth following injury. The thin-film meshmembrane or hybrid membrane would have channels aligned like a nativenerve to facilitate axon growth in a controlled manner.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used inreconstructive or cosmetic surgery to replace ligaments because of theelastic properties of thin-film mesh (e.g., breast tissue containsmultiple small ligamentous elements that give rise to the shape andmechanical properties of the organ, and post-mastectomy prostheses,i.e., breast implants, are essentially non-structured bags of saline,silicone gel, or other materials).

In some embodiments, thin-film mesh membranes, thin-film meshstructures, and/or corresponding hybrid membranes/structures can bejoined together to create the basis for more complex cartilaginousstructures (e.g., external ear, portions of nose) when seeded withchondrocytes.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used toreplace elements of the eye that have been injured traumatically or bydisease (e.g., a tumor).

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used toconstruct replacement elements of the bronchial tree in the lungs.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure composed of orincluding Nitinol may be seeded with myocytes to construct replacementskeletal muscle. Because Nitinol has the ability to change shape whenelectrical current is passed through it, it may be advantageously beused in artificial limbs.

In some embodiments, a thin-film mesh membrane, a thin-film meshstructure, or a corresponding hybrid membrane/structure may be used as ameans to deliver both small and large molecules (i.e. proteins) toanatomical sites of interest.

Embodiments described herein illustrate but do not limit the disclosure.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the presentdisclosure. Accordingly, the scope of the disclosure is best definedonly by the following claims.

What is claimed is:
 1. A thin-film micromesh device comprising: abackbone extending in a longitudinal axis; and a thin-film micromeshassembled on the backbone, the thin-film micromesh comprising one ofmore slits elongated in a slit axis, wherein the slit axis is angledfrom the longitudinal axis.
 2. The thin-film micromesh device of claim1, wherein the one or more slits are expandable in an expansion axisperpendicular to the slit axis.
 3. The thin-film micromesh device ofclaim 1, wherein the thin-film micromesh device has a cylindrical shape,and wherein the one or more slits are expanded such that the thin-filmmicromesh is expandable both along the longitudinal axis of thecylindrical shape thin-film micromesh and along a circumferentialdirection of the cylindrical shape thin-film micromesh.
 4. The thin-filmmicromesh device of claim 3, wherein the thin-film micromesh isexpandable along the circumferential direction allowing the cylindricalshape thin-film micromesh device to expand radially increasing adiameter of the cylindrical shape thin-film micromesh device.
 5. Thethin-film micromesh device of claim 3, wherein an angle formed betweenthe slit axis and the longitudinal axis determines an expandability ofthe thin-film micromesh along the longitudinal axis relative to anexpandability of the thin-film micromesh in the circumferentialdirection.
 6. The thin-film micromesh device of claim 1, wherein thethin-film micromesh comprises thin-film Nitinol (TFN).
 7. The thin-filmmicromesh device of claim 1, wherein the one or more slits are arrangedin series in a diagonal row parallel to the slit axis.
 8. The thin-filmmicromesh device of claim 7, wherein diagonal rows of slits are arrangedin parallel to form a longitudinal column of slits.
 9. The thin-filmmicromesh device of claim 1, wherein the one or more slits comprise afirst type slit elongated in a first slit axis forming a first anglewith the longitudinal axis and a second type slit elongated in a secondslit axis forming a second angle with the longitudinal axis.
 10. Thethin-film micromesh device of claim 9, wherein the first type slit is amirror image of the second type slit with respect to the longitudinalaxis.
 11. The thin-film micromesh device of claim 9, wherein the firstangle equals the second angle, but the first type slit and the secondtype slit are angled from the longitudinal axis in opposite directions.12. The thin-film micromesh device of claim 9, wherein the first typeslit is provided in a first longitudinal column and the second type slitis provided in a second longitudinal column adjacent to the firstlongitudinal column.
 13. The thin-film micromesh device of claim 12,wherein the first type slit and the second type slit form a V-shape atan interface between the first and the second longitudinal columns. 14.The thin-film micromesh device of claim 13, wherein an angle formed bythe V-shape determines an expandability of the thin-film micromesh alongthe longitudinal axis relative to an expandability of the thin-filmmicromesh in the circumferential direction.
 15. The thin-film micromeshdevice of claim 14, wherein increasing the angle formed by the V-shapeincreases the expandability of the thin-film micromesh along thelongitudinal axis relative and decreases the expandability of thethin-film micromesh in the circumferential direction.
 16. The thin-filmmicromesh device of claim 9, wherein the thin-film micromesh comprisesfirst type longitudinal columns comprising first type slits and secondtype longitudinal columns comprising second type slits, wherein thefirst type longitudinal columns and the type longitudinal column arearranged around the thin-film micromesh in an alternating matter, suchthat the first type slits and the second type slits form a zig-zappattern around the thin-film micromesh.
 17. The thin-film micromeshdevice of claim 16, wherein the first type slits and the second typeslits are a mirror image of each other and the zig-zag pattern providessymmetrical or uniform expansion of the thin-film micromesh.
 18. Thethin-film micromesh device of claim 8, wherein a number of slits in thediagonal rows determines a force required to expand the thin-filmmicromesh.
 19. A method comprising: deep reactive ion etching amicropattern of trenches on a surface of a substrate, the trenchescorresponding to angled slits in a thin-film micromesh to be formed;depositing a lift-off layer on the etched substrate; depositing a firstNitinol layer over the lift-off layer; and etching the lift-off layer toform the thin-film micromesh.
 20. The method of claim 1, furthercomprising: depositing a bonding layer on at least one area of the firstNitinol layer; depositing a sacrificial layer on a remaining area of thefirst Nitinol layer; depositing a second Nitinol layer on the bondinglayer and the sacrificial layer; and annealing the first Nitinol layerand the second Nitinol layer with the bonding layer; wherein the etchingfurther etches the sacrificial layer to form the thin-film micromeshhaving a three dimensional shape.